requires that the sequence does not have any other configuration with a comparable free energy.

stability

small changes in the surrounding environment cannot give rise to changes in the minimum configuration.

kinetical accessibility

means the final shape can be got without going through any highly complex changes in the shape (like knots, for example).

How the protein reaches this structure is the subject of the field of protein folding, which has a related dogma called Levinthal's paradox. The Levinthal paradox states that the number of possible conformations available to a given protein is astronomically large, such that even a small protein of 100 residues would require more time than the universe has existed to explore all possible conformations (1026 seconds) and choose the appropriate one.